Shares of Illumina Inc. /zigman2/quotes/203509482/composite ILMN -5.97% dropped 5.3% in premarket trading Monday, after the gene sequencing company confirmed a deal to buy Grail Inc. for $8 billion in cash and stock. The Wall Street Journal reported earlier that an announcement of the deal, in which Illumina pays $7.1 billion for the part of Grail it doesn't already own, would be announced Monday. The report said the deal for the developer of a blood test that helps detect cancer, is expected to be announced Monday. Illumina said the deal includes $3.5 billion in cash and $4.5 billion in Illumina shares. "GRAIL extends Illumina's portfolio to include cancer screening, diagnosis and cancer monitoring, creating a portfolio of best-in-class, proprietary tests in each of the major oncology testing application areas," Illumina said in a statement. The stock has dropped 10.9% year to date through Friday, while the iShares Nasdaq Biotechnology ETF /zigman2/quotes/206189322/composite IBB -2.22% has rallied 13.1% and the S&P 500 /zigman2/quotes/210599714/realtime SPX -1.54% has gained 2.8%.